title: Evaluation of virulence and antimicrobial resistance in Salmonella enterica serovar Enteritidis isolates from humans and chicken- and egg-associated sources.
abstract: Salmonella enterica serovar Enteritidis is a leading cause of salmonellosis throughout the world and is most commonly associated with the consumption of contaminated poultry and egg products. Salmonella Enteritidis has enhanced ability to colonize and persist in extraintestinal sites within chickens. In this study, 54 Salmonella Enteritidis isolates from human patients (n=28), retail chicken (n=9), broiler farms (n=9), and egg production facilities (n=8) were characterized by antimicrobial susceptibility testing, plasmid analysis, genetic relatedness using XbaI and AvrII pulsed-field gel electrophoresis (PFGE), and the presence of putative virulence genes. Nine isolates were evaluated for their abilities to invade and survive in intestinal epithelial and macrophage cell lines. Overall, 56% (n=30) of isolates were resistant to at least one antimicrobial agent tested, yet no isolates showed resistance to more than three antimicrobials. All isolates carried a common ∼55-kb plasmid, with some strains containing additional plasmids ranging from 3 to 50 kb. PFGE analysis revealed five XbaI and AvrII clusters. There were significant overlaps in the PFGE patterns of the isolates from human, chicken, and egg houses. All isolates tested PCR positive for iacP, purR, ttrB, spi4H, rmbA, sopE, invA, sopB, spvB, pagC, msgA, spaN, orgA, tolC, and sifA, and negative for iss, virB4, and sipB. Of the isolates selected for virulence testing, those containing the iron acquisition genes, iutA, sitA, and iucA, and ∼50-kb plasmids demonstrated among the highest levels of macrophage and epithelial cell invasion, which may indicate their importance in pathogenesis.
authors.affiliation: 1 Division of Microbiology, National Center for Toxicological Research , U.S. Food and Drug Administration, Jefferson, Arkansas.
authors.forename: Jing
authors.initials: J
authors.lastname: Han
authors.forename: Kuppan
authors.initials: K
authors.lastname: Gokulan
authors.forename: Dustyn
authors.initials: D
authors.lastname: Barnette
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Khare
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Rooney
authors.forename: Joanna
authors.initials: J
authors.lastname: Deck
authors.forename: Rajesh
authors.initials: R
authors.lastname: Nayak
authors.forename: Rossina
authors.initials: R
authors.lastname: Stefanova
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hart
authors.forename: Steven L
authors.initials: SL
authors.lastname: Foley
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002460:Cell Line; D002645:Chickens / Q000382:microbiology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000235:genetics; D004531:Eggs / Q000382:microbiology; D016521:Electrophoresis, Gel, Pulsed-Field; D004847:Epithelial Cells / Q000382:microbiology; D005243:Feces / Q000382:microbiology; D014644:Genetic Variation; D006801:Humans; D008264:Macrophages / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D011201:Poultry Diseases / Q000382:microbiology*; D051381:Rats; D012478:Salmonella Food Poisoning / Q000382:microbiology; D012480:Salmonella Infections / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012477:Salmonella enteritidis / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D037521:Virulence Factors